US President Donald Trump asked then-FBI Director James Comey to shut down an investigation into ties between then-White House national security adviser Michael Flynn and Russia, the NewYorkTimes reports, citing a James Comey memo.

"I hope you can let this go," Mr Trump told Mr Comey, according to two people who read the memo, the Times reported.

An associate of Mr Comey who has seen the memo told Reuters that the details of the document as reported by the New York Times were accurate.

Michael Flynn

A retired US lieutenant-general. Joined the Trump presidential campaign in mid-2016. In November 2016 took Mr Trump's offer of National Security Advisor role.

In December Flynn spoke with the Russian ambassador and later denied reports they had talked.

In February 2017, Flynn resigned after reports he had misled the Vice President about negotiating with Russia.

James Comey

Director of FBI since 2013. In July 2016, during the presidential race, Comey announced the FBI recommendation that no criminal charges be laid against Hillary Clinton.

In late October 2016, two weeks before the US election, Comey announced an additional investigation regarding Hillary Clinton's emails. After a few days the FBI found nothing, but Clinton did attribute her loss to the timing of Comey's announcement.

In July 2016, Comey and the FBI also opened an investigation into the Trump campaign's connection to Russian interference in the election.

In May 2017, Comey was fired from his role leading the FBI, just a few days after asking the Justice Department for more funding and personnel in the Russia investigation.

The White House says the report is "not a truthful or accurate portrayal of the conversation between the President and Mr Comey."

It says that while the President has repeatedly expressed his view that Flynn is a "decent man," he has never asked Comey or anyone else to end any investigations involving him.